Nonwoven materials span a diverse range of physical properties and are widely used for a variety of diverse products. Some examples of nonwoven products are, disposable clothing, geo-textiles, insulation, filters, carpet underlay or backing, pillows cushions and upholstery padding and disposable absorbent hygiene articles such as diapers, training pants, female pads and tampons, both wet and dry wipes as well as adult incontinence products.
Nonwoven materials or webs can be manufactured from a wide range of different fibers both man made (synthetic) and natural but the majority are constructed from man made fibers and in particular polypropylene and polyesters (mainly PET).
Nonwoven materials can be manufactured via a range of processes, including wet laying and dry laying techniques such as carding, spun-laying, and air-laying followed by a bonding process to add strength. Although not limited to, this is typically achieved via four different general process types, thermal bonding, hydroentanglement, needlefelt (or needlepunch) and chemical or adhesive bonding.
While the market for nonwoven materials for articles of clothing and hygienic articles such as diapers, wipes and pads, has been largely dominated by the use of predominantly synthetic fiber webs, nonwovens constructed from entirely natural fibers are not unknown.
Nonwovens manufactured from cellulosic fibers like cotton are known in the art. For example U.S. Pat. No. 5,199,134, which discloses a system and method for producing a bleached cotton, nonwoven web.
Natural fibers like cotton are particularly prized because they yield webs that are absorbent and soft compared with the equivalent synthetic webs. Natural fibers such as cotton fibers are also biodegradable. These properties have particularly lead to their use in medical applications such as disposable sheets, blankets, surgical gowns and bandages.
Natural fibers like cotton are also desirable for use in the manufacture of nonwoven products, such as in disposable absorbent hygiene articles such as diapers, training pants, female pads and tampons, both wet and dry wipes and adult incontinence products, as they are perceived to be softer and more environmentally friendly by consumers.
It is also desirable, when manufacturing disposable absorbent hygiene articles to utilize hydroentanglement when bonding the fibers in the web. Without being bound by theory, it is believed that hydroentanglement processes yield webs which are softer and have increased drape relative to other known bonding processes, such as thermal-bonding and adhesive bonding.
However hydroentanglement of pure cotton nonwovens is known to result in nonwovens which are mechanically weak and typically have a low resistance to abrasion when wet. Cotton fibers may be blended with synthetic fibers to improve the mechanical properties of the resulting nonwovens. Alternatively binders or resins can be added to improve the durability of the products. U.S. Pat. No. 5,393,304 details using 0.2-1% by weight of a polyamide-amine-epichlorohydrin (PAE) resin on cotton based nonwovens to enable them to be repeatedly laundered without disintegration.
Separately, cotton fibers can be acquired from a number of sources. These sources include, but are not limited to, virgin or fresh cotton fibers and recycled or reclaimed cotton fibers. For example, US 2002/0124366 discloses a system for reconstituting fibers from recycled waste fabric material, including cotton denim waste. The fibers are returned to a substantially virgin state and can be successfully incorporated into hydroentangled or needlepunched nonwoven products without the need for binders or additives.